Planetary gear transmission system

Abstract

A planetary gear transmission gear system comprises a main planetary gear train composed of a main sun gear, a main ring gear, and main planet gears. The main sun gear is driven by an input rotary shaft to rotate. A sub planetary gear train is included to have a sub sun gear, a sub ring gear, and sub planet gears, and has a different gear ratio from the main planetary gear train. The sub sun gear is connected to rotate together with the main sun gear. A common carrier supporting the main and sub planet gears is rotatable about a common center axis and is drivingly connected to rotate an output shaft. A lock mechanism releasably fixes the main ring gear in order to allow the main planet gears to rotate about the center axis as the main sun gear rotates with the main ring gear fixed. A one-way clutch is connected to permit the sub ring gear to rotate in a first direction and to prohibit the sub ring gear from rotating in a second direction opposite to the first direction. The first direction is selected to be a direction in which the sub ring gear is permitted to rotate while the carrier rotates with the main ring gear fixed by the lock mechanism such that the sub ring gear is locked in the second direction after the main ring gear is released, thereby permitting the carrier to continue rotating at a speed reduction ratio different than when the main ring gear is fixed.

What is claimed is: 
     
       1. A planetary gear transmission system, comprising: a main planetary gear train composed of a main sun gear (21), a main hollow gear (22) coaxial with said main sun gear, and main planet gears (23) meshing with said main sun gear and said main hollow gear, said main sun gear having means for direct connection to an input rotary shaft (2) of an electric motor to rotate;   a sub planetary gear train composed of a sub sun gear (31), a sub hollow gear (32) coaxial with said sub sun gear, and sub planet gears (33) meshing with said sub sun gear and said sub hollow gear and having a different gear ratio than said main planetary gear train, said sub sun gear connected to said main sun gear to rotate together therewith;   a common carrier (40) supporting said main and sub planet gears (23, 33) and rotatable about a common center axis of said main and sub sun gears (21, 31), said common carrier adapted in use to be drivingly connected to an output shaft (5);   lock means (60, 61) for locking said main hollow gear and releasing the same, wherein said main planetary gear train has a lower reduction ratio than the sub planetary gear train; and   first one-way clutch means (70) which is connected to said sub hollow gear (32) to permit said sub hollow gear to rotate in a first direction and to prohibit said sub hollow gear from rotating in a second direction opposite to said first direction, said first direction being selected to be a direction in which said sub hollow gear (32) is permitted to rotate during said common carrier (40) rotates, while said main hollow gear (22) is fixed by said lock means, such that said sub hollow gear (32) is locked in said second direction after said main hollow gear (22) is released to thereby permit said common carrier (40) to continue rotating at a speed reduction ratio different than when said main hollow gear is fixed.   
     
     
       2. A planetary gear transmission system as set forth in claim 1, wherein said one-way clutch means (70) includes direction switch means (73, 77) for switching said first and second directions. 
     
     
       3. A planetary gear transmission system as set forth in claim 2, wherein said one-way clutch means (70) comprises a fixed outer race (10), an inner race integral with said sub hollow gear (32), and a roller (71) received in each one of first and second compartments (74, 75) formed to extend circumferentially between said outer and inner races, and wherein said direction switch means comprises a switch member (73) for displacing said rollers (71) circumferentially in said first and second compartments (74, 75) between a first position and a second position, said first and second compartments having varying gap between said inner and outer races to define a lock end in one of circumferential ends of each compartment and a release end in the other circumferential end thereof, said lock ends of said first and second compartments opposing to each other in the circumferential direction, said lock end having a gap smaller than the diameter of said roller (71) and said release end having a gap greater than the diameter of said roller (71), said roller movable circumferentially in each compartment (74, 75) and urged towards said lock end such that said roller (71) in said first compartments (74) is displaced into said lock end to permit said inner race (32) to rotate only in said first direction when said switch member (73) is moved to said first position, and that said roller (71) in said second compartment (75) is displaced into said lock end to permit said inner face (32) to rotate only in said second direction when said switch member (73) is moved to said second position. 
     
     
       4. A planetary gear transmission system as set forth in claim 3, wherein said first and second compartments (74, 75) are formed as a continuous space between said outer race (10) and said inner race (32) and separated by said switch member (73) received in said space, said rollers (71) in said first and second compartments (74, 75) being urged against said switch member (73). 
     
     
       5. A planetary gear transmission system as set forth in claim 1, further comprising an additional sub hollow gear (132) meshing with said sub planet gears (33A) in a coaxial relation with said sub hollow gear (32A); and second one-way clutch means (170), which is connectable to said additional sub hollow gear (132) to permit said additional sub ring to rotate only in the second direction, wherein selector means (120) is provided to selectively actuate said first and second one-way clutch means. 
     
     
       6. A planetary gear transmission system as set forth in claim 1, wherein said lock means (60, 61; 60A, 61A) is movable from a lock position of fixing said main hollow gear (22, 22A) to a release position of releasing said main hollow gear, said lock means being actuated to move into said release position in response to said main hollow gear receiving a load which exceeds a predetermined level. 
     
     
       7. A planetary gear transmission system as set forth in claim 1, wherein said lock means (60, 61) is movable from a lock position of fixing said main hollow gear (22) to a release position of releasing said main hollow gear, and a release handle is connected to manually move said lock means into said release position. 
     
     
       8. A planetary gear transmission system as set forth in claim 1, wherein said lock means (60, 61) is movable from a lock position of fixing said main hollow gear (32) to a release position of releasing said main hollow gear, and an electromagnetic actuator (80) is connected to move said lock means into said release position in response to an electric signal. 
     
     
       9. A planetary gear transmission system as set forth in claim 8, wherein said electromagnetic actuator comprises a keep solenoid (80) with a plunger (81) connected to move said lock means (60), said keep solenoid actuated by an application of an electric current to move said lock means into said release position and holding said lock means in said lock position in the absence of the electric current. 
     
     
       10. A planetary gear transmission system as set forth in claim 9, wherein said keep solenoid (80) includes a permanent magnet attracting said plunger (81) in the direction of holding said lock means in said lock position, and wherein spring means (82) is connected to urge said plunger in the direction of moving said lock means to said release position against the magnetic attraction of said permanent magnet and holds said lock means in said release position after said lock means moves to said release position from said lock position. 
     
     
       11. A planetary gear transmission system as set forth in claim 9, wherein said keep solenoid (80) includes a permanent magnet attracting said plunger (81) in the direction of moving said lock means in said release position, and wherein spring means is connected to urge said plunger in the direction of moving said lock means to said lock position, said keep solenoid acting when energized by an electric current to actuate said plunger against the bias of said spring means in the direction of moving said lock means towards the release position in which said plunger is held in position by the attraction of the said permanent magnet. 
     
     
       12. A planetary gear transmission system as set forth in claim 9, wherein said carrier (40) rotates at a lower speed reduction ratio when said lock means is at said lock position of fixing said main hollow gear (22) than when said lock means is moved to said release position of releasing said main hollow gear to correspondingly fix said sub hollow gear (32), and wherein said keep solenoid (80) is connected to a return handle (83) by which said lock means is manually operated to move from said release position to said lock position. 
     
     
       13. A planetary gear transmission system as set forth in claim 12, wherein said keep solenoid (80) is actuated to move said lock means (60, 61) from said lock position to said release position in response to said output shaft (5) receiving a load which exceeds a predetermined level, and wherein said return handle (83) is connected to a trigger (90) of a power tool incorporating said system so that said return handle (83) is actuated to return said lock means back to said lock position each time said trigger (90) is actuated to operate said power tool. 
     
     
       14. A planetary gear transmission system as set forth in claim 1, wherein said one-way clutch means (70) comprises a fixed outer race (10), an inner race integral with said sub hollow gear (32), and a roller (71) held between said outer and inner races to allow said inner race to rotate only in said first direction, said outer race being formed as a part of a gear casing (10) incorporating said main and sub planetary gear trains, and said inner race defining itself said sub hollow gear (32). 
     
     
       15. A planetary gear transmission system, comprising: a main planetary gear train composed of a main sun gear, a main ring gear coaxial with said main sun gear, and main planet gears meshing with said main sun gear and said main ring gear, said main sun gear adapted in use to be connected to an input rotary shaft to be driven thereby to rotate;   a sub planetary gear train composed of a sub sun gear, a sub ring gear coaxial with said sub sun gear, and sub planet gears meshing with said sub sun gear and said sub ring gear and having a different gear ratio than said main planetary gear train, said sub sun gear connected to said main sun gear to rotate together therewith;   a common carrier supporting said main and sub planet gears and rotatable about a common center axis of said main and sub sun gears, said common carrier adapted in use to be drivingly connected to an output shaft;   lock means for releasably fixing said main ring gear;   first one-way clutch means, connected to said sub ring gear for permitting said sub ring gear to rotate in a first direction and for preventing said sub ring gear from rotating in a second direction opposite to said first direction, said first direction being selected to be a direction in which said sub ring gear is permitted to rotate during said common carrier rotation with said main ring gear fixed by said lock means, such that said sub ring gear is locked in said second direction after said main ring gear is released to thereby permit said common carrier to continue rotating at a speed reduction ratio different than when said main ring gear is fixed;   an additional sub ring gear meshing with said sub planet gears in a coaxial relation with said sub ring gear; and   second one-way clutch means which is connectable to said additional sub ring gear to permit said additional sub ring to rotate only in the second direction, wherein selector means is provided to selectively actuate said first and second one-way clutch means.   
     
     
       16. A planetary gear transmission system, comprising: a main planetary gear train composed of a main sun gear, a main ring gear coaxial with said main sun gear, and main planet gears meshing with said main sun gear and said main ring gear, said main sun gear adapted in use to be connected to an input rotary shaft to be driven thereby to rotate;   a sub planetary gear train composed of a sub sun gear, a sub ring gear coaxial with said sub sun gear, and sub planet gears meshing with said sub sun gear and said sub ring gear and having a different gear ratio than said main planetary gear train, said sub sun gear connected to said main sun gear to rotate together therewith;   a common carrier supporting said main and sub planet gears and rotatable about a common center axis of said main and sub sun gears, said common carrier adapted in use to be drivingly connected to an output shaft;   lock means for releasably fixing said main ring gear; and   first one-way clutch means, connected to said sub ring gear for permitting said sub ring gear to rotate in a first direction and for preventing said sub ring gear from rotating in a second direction opposite to said first direction, said first direction being selected to be a direction in which said sub ring gear is permitted to rotate during said common carrier rotation with said main ring gear fixed by said lock means, such that said sub ring gear is locked in said second direction after said main ring gear is released to thereby permit said common carrier to continue rotating at a speed reduction ratio different than when said main ring gear is fixed,   wherein said lock means is movable from a lock position of fixing said main ring gear to a release position of releasing said main ring gear, said lock means being actuated to move into said release position in response to said main ring gear receiving a load which exceeds a predetermined level.   
     
     
       17. A planetary gear transmission system, comprising: a main planetary gear train composed of a main sun gear, a main ring gear coaxial with said main sun gear, and main planet gears meshing with said main sun gear and said main ring gear, said main sun gear adapted in use to be connected to an input rotary shaft to be driven thereby to rotate;   a sub planetary gear train composed of a sub sun gear, a sub ring gear coaxial with said sub sun gear, and sub planet gears meshing with said sub sun gear and said sub ring gear and having a different gear ratio than said main planetary gear train, said sub sun gear connected to said main sun gear to rotate together therewith;   a common carrier supporting said main and sub planet gears and rotatable about a common center axis of said main and sub sun gears, said common carrier adapted in use to be drivingly connected to an output shaft;   lock means for releasably fixing said main ring gear; and   first one-way clutch means, connected to said sub ring gear for permitting said sub ring gear to rotate in a first direction and for preventing said sub ring gear from rotating in a second direction opposite to said first direction, said first direction being selected to be a direction in which said sub ring gear is permitted to rotate during said common carrier rotation with said main ring gear fixed by said lock means, such that said sub ring gear is locked in said second direction after said main ring gear is released to thereby permit said common carrier to continue rotating at a speed reduction ratio different than when said main ring gear is fixed,   wherein said lock means is movable from a lock position of fixing said main ring gear to a release position of releasing said main ring gear, and release handle is connected to manually move said lock means into said release position.   
     
     
       18. A planetary gear transmission system, comprising: a main planetary gear train composed of a main sun gear, a main ring gear coaxial with said main sun gear, and main planet gears meshing with said main sun gear and said main ring gear, said main sun gear adapted in use to be connected to an input rotary shaft to be driven thereby to rotate;   a sub planetary gear train composed of a sub sun gear, a sub ring gear coaxial with said sub sun gear, and sub planet gears meshing with said sub sun gear and said sub ring gear and having a different gear ratio than said main planetary gear train, said sub sun gear connected to said main sun gear to route together therewith;   a common carrier supporting said main and sub planet gears and rotatable about a common center axis of said main and sub sun gears, said common carrier adapted in use to be drivingly connected to an output shaft;   lock means for releasably fixing said main ring gear; and   first one-way clutch means, connected to said sub ring gear for permitting said sub ring gear to rotate in a first direction and for preventing said sub ring gear from routing in a second direction opposite to said first direction, said first direction being selected to be a direction in which said sub ring gear is permitted to rotate during said common carrier rotation with said main ring gear fixed by said lock means, such that said sub ring gear is locked in said second direction after said main ring gear is released to thereby permit said common carrier to continue rotating at a speed reduction ratio different than when said main ring gear is fixed,   wherein said lock means is movable from a lock position of fixing said main ring gear to a release position of releasing said main ring gear, and an electromagnetic actuator is connected to move said lock means into said release position in response to an electric signal.   
     
     
       19. A planetary gear transmission system as set forth 18, wherein said electromagnetic actuator comprises a keep solenoid with a plunger connected to move said lock means, said keep solenoid actuated by an application of an electric current to move said lock means into said release position and holding said lock means in said lock position in the absence of the electric current. 
     
     
       20. A planetary gear transmission system as set forth in claim 19, wherein said keep solenoid includes a permanent magnet attracting said plunger in the direction of holding said lock means in said lock position, and wherein spring means is connected to urge said plunger in the direction of moving said lock means to said release position against the magnetic attraction of said permanent magnet and holds said lock means in said release position after said lock means moves to said release position from said lock position. 
     
     
       21. A planetary gear transmission system as set forth in claim 19, wherein said keep solenoid includes a permanent magnet attracting said plunger in the direction of moving said lock means in said release position, and wherein spring means is connected to urge said plunger in the direction of moving said lock means to said lock position, said keep solenoid acting when energized by an electric current to actuate said plunger against the bias of said spring means in the direction of moving said lock means towards the release position in which said plunger is held in position by the attraction of the said permanent magnet. 
     
     
       22. A planetary gear transmission system as set forth in claim 19, wherein said carrier rotates at a lower speed reduction ratio when said look means is at said lock position of fixing said main ring gear than when said lock means is moved to said release position of releasing said main ring gear to correspondingly fix said sub ring gear, and wherein said keep solenoid is connected to a return handle by which said look means is manually operated to move from said release position to said lock position. 
     
     
       23. A planetary gear transmission system as set forth in claim 22, wherein said keep solenoid is actuated to move said lock means from said lock position to said release position in response to said output shaft receiving a load which exceeds a predetermined level, and wherein said return handle is connected to a trigger of a power tool incorporating said system so that said return handle is actuated to return said lock means back to said lock position each time said trigger is actuated to operate said power tool. 
     
     
       24. A planetary gear transmission system, comprising: a main planetary gear train composed of a main sun gear, a main ring gear coaxial with said main sun gear, and main planet gears meshing with said main sun gear and said main ring gear, said main sun gear adapted in use to be connected to an input rotary shaft to be driven thereby to rotate; a sub planetary gear train composed of a sub sun gear, a sub ring gear coaxial with said sub sun gear, and sub planet gears meshing with said sub sun gear and said sub ring gear and having a different gear ratio than said main planetary gear train, said sub sun gear connected to said main sun gear to rotate together therewith;   a common carrier supporting said main and sub planet gears and rotatable about a common center axis of said main and sub sun gears, said common carrier adapted in use to be drivingly connected to an output shaft;   lock means for releasably fixing said main ring gear; and   first one-way clutch means, connected to said sub ring gear for permitting said sub ring gear to rotate in a first direction and for preventing said sub ring gear from rotating in a second direction opposite to said first direction, said first direction being selected to be a direction in which said sub ring gear is permitted to rotate during said common carrier rotation with said main ring gear fixed by said lock means, such that said sub ring gear is locked in said second direction after said main ring gear is released to thereby permit said common carrier to continue rotating at a speed reduction ratio different than when said main ring gear is fixed,   wherein said one-way clutch means comprises a fixed outer race, an inner race integral with said sub ring gear, and a roller held between said outer and inner races to allow said inner race to rotate only in said first direction, said outer race being formed as part of a gear casing incorporating said main and sub planetary gear trains, and said inner race defining itself said sub ring gear.   
     
     
       25. A planetary gear transmission system, comprising: a main planetary gear train composed of a main sun gear, a main ring gear coaxial with said main sun gear, and main planet gears meshing with said main sun gear and said main ring gear, said main sun gear adapted in use to be connected to an input rotary shaft to be driven thereby to rotate;   a sub planetary gear train composed of a sub sun gear, a sub ring gear coaxial with said sub sun gear, and sub planet gears meshing with said sub sun gear and said sub ring gear having a different gear ratio than said main planetary gear train, said sub sun gear connected to said main sun gear to rotate together therewith;   a common carrier supporting said main and sub planet gears and rotatable about a common center axis of said main and sub sun gears, said common carrier adapted in use to be drivingly connected to an output shaft;   lock means for releasably fixing said main ring gear; and   first one-way clutch means, connected to said sub ring gear for permitting said sub ring gear to rotate in a first direction and for preventing said sub ring gear from rotating in a second direction opposite to said first direction, said first direction being selected to be a direction in which said sub ring gear is permitted to rotate during said common carrier rotation with said main ring gear fixed by said lock means, such that said sub ring gear is locked in said second direction after said main ring gear is released to thereby permit said common carrier to continue rotating at a speed reduction ratio different than when said main ring gear is fixed,   wherein said one-way clutch means includes direction switch means for switching said first and second directions, and   wherein said one-way clutch means comprises a fixed outer race, an inner race integral with said sub ring gear, and a roller received in each one of first and second compartments formed to extend circumferentially between said outer and inner races, and wherein said direction switch means comprises a switch member for displacing said rollers circumferentially in said first and second compartments between a first position and a second position, said first and second compartments having varying gap between said inner and outer races to define a lock end in one of circumferential ends of each compartment and a release end in the other circumferential end thereof, said lock ends of said first and second compartments opposing to each other in the circumferential direction, said lock end having a gap smaller than the diameter of said roller and said release end having a gap greater than the diameter of said roller, said roller movable circumferentially in each compartment and urged towards said lock end such that said roller in said first compartments is displaced into said lock end to permit said inner race to rotate only in said first direction when said switch member is moved to said first position, and that said roller in said second compartment is displaced into said lock end to permit said inner face to rotate only in said second direction when said switch member is moved to said second position.   
     
     
       26. A planetary gear transmission system as set forth in claim 25, wherein said main and sub planetary gear trains are configured such that said carrier rotates at a higher speed reduction ratio with said sub ring gear being fixed than with said main ring gear being fixed. 
     
     
       27. A planetary gear transmission system as set forth in claim 25, wherein said first and second compartments are formed as a continuous space between said outer race and said inner race and separated by said switch member received in said space, said rollers in said first and second compartments being urged against said switch member.